There has been a need to find microbes in relatively large volumes of fluid, observe the activity, and identify the species. Some of the microbes that can be monitored include giardia, salmonella, escherichia coli, isochrysis, to name a few. Such fluids are, but not limited to, waste water or blood. The prior art used a system of placing a fluid sample on a glass slide and then sandwiching the sample by placing another glass slide on top of the fluid and viewing the sample with a microscope. There are a number of problems with this technique. The samples would die for lack of adequate gas exchange shortly after placement of the second slide which necessitated an immediate monitoring. The sample was also restricted to a very small volume of fluid because the top slide would displace the sample. It was virtually impossible to observe all the different types of microbe activity in the fluid. In instances where the need was to ascertain the presence or absence of a few microbes in, for example, a sample drawn from a reservoir, the very small fluid volume made direct microscopic observation useless.
There have been articles written about tracking microbes. The closest reference is a paper written by A. T. Cheung, "Quantitative Microscopy: A micro-image-analysis approach to characterize and quantitate biomotility" published in Engineering Science, Fluid Dynamics, by World Publishing Company, 1990. The article describes an optical-digital system to track the motion of microbes. The system is based on a microscope, a video camera and a computer processing system. Because that system uses a microscope to extract information describing motility, it can not monitor and track the motion of microbes in their natural state and in real-time. The limitation of that system has been mentioned in the first paragraph. Other references that relate to the tracking but are not as relevant as the paper written by A. T. Cheung are:
(1) D. Z. Anderson, D. M. Lininger, Optical tracking novelty filter, Optics Letters, Vol. 12, p. 123, 1987.
(2) Y. Li, A. Kostrzewski, D. H. Kim, Liquid crystal TV-based white light optical tracking novelty filter, Applied Optics, Vol. 28, p. 4861, 1989.
(3) N. George, S. G. Wang, D. L. Venable, Pattern recognition using the ring-wedge detector and neural-network software, SPIE, Vol. 1134, p. 96, 1989.
(4) E. C. Tam, Autonomous real-time object tracking with an adaptive joint transform correlator, Optical Engineering, Vol. 29, p. 314, 1990.
A number of articles of interest dealing with this subject are in a text entitled "The Application of Laser Light Scattering to the Study of Biological Motion" edited by J. C. Ernshaw and M. W. Steer, copyright 1990, Plenum Publishing Corp. Several articles in this text deal with laser light measurements of motility of living cells and microorgansims, with particular reference being made to the article by J. S. Ernshaw entitled "Laser Doppler Velocimetry" which describes a differential laser doppler in which one of the beams was electronically down mixed to give effective frequency shifts as low as 10 kHz, and the article by J. P. Boon entitled "Motility of Living Cells and Microorganisms" which describes the effect of stimuli on the motility of cells.